Sponges are light, fibrous connective structures which have absorbent qualities. They can be made from a variety of different materials including polymers such as urethanes and cellulose in a number of different ways.
A preferred sponge is the cellulose sponge because of its excellent water sorption qualities. These sponges are made by dispersing sodium sulfate crystals in a viscose cellulose. Once mixed with the viscose cellulose, the sodium sulfate crystals are melted out of the sponge by heating the viscose cellulose while the viscose cellulose is regenerated or coagulated to an insoluble state. Once regenerated, the viscose cellulose sponge is rinsed.
Although exhibiting excellent water sorption qualities superior to other sponges, cellulose sponges have several drawbacks due to this characteristic. One drawback is that sponges can absorb moisture containing unwanted microorganisms such as bacteria and fungi. These microorganisms thrive and rapidly multiply in the moist environment found in the sponge and can degrade the sponge by causing loss in sponge strength and integrity. In addition, the microorganisms can emit an odor which is unpleasant to a sponge user.
Moreover, many of these microorganisms are pathogenic thereby raising health and safety concerns. Pathogenic microorganisms such as gram negative bacteria, gram positive bacteria, yeast and fungi have all been found in sponges. Such concerns are especially relevant in the food service and medical industries where sanitization and the prevention of the spread infectious disease is of utmost importance. For example, in the food service industry, salmonella choleraesuis can be transferred to a sponge from a surface contacted by the sponge. The salmonella choleraesuis can then multiply in the sponge and be transferred to another surface thereby increasing the chance of infection.
Several attempts have been made to control or prevent the growth of these unwanted microorganisms in cellulosic sponges by treating the sponges with anti-microbial agents such as biocides. For example, U.S. Pat. No. 3,018,192 ("Hennemann et al.") discloses the use of a reaction product of a quaternary ammonium compound with either an alkali metal salt or carboxymethyl cellulose as the biocide.
U.S. Pat. No. 3,594,221 ("Baldwin") describes another process of treating fibrous materials with a germicide such as a quaternary ammonium compound. In this process, the fibrous materials are first impregnated with an acid or alkali metal montmorillonite clay. Once impregnated with the clay, the materials are infused with the germicide.
Another attempt to prevent microorganism growth in sponges and other cellulose-based products is described in EPO No. 358,572 ("Collin"). Collin discloses a post-regenerative treatment imparting biocidal properties to porous cellulose-based products. The cellulose-based products are impregnated with a solution containing an aqueous biocide such as a quaternary ammonium compound or an oligomeric polyalkylene-2-guanide salt. The solution also contains a binder such as an acrylic latex, butadiene-styrene latex or vinylic latex. After impregnation, a second solution is contacted with the cellulose-based product. This second solution precipitates the biocidal agent onto the porous surfaces of the cellulose-based product and in addition, coagulates the binder.
A different biocidal sponge treatment is described in U.S. Pat. No. 3,586,520. ("Dillon"). Dillon teaches that metal dialkyl dithiocarbamates can be utilized as biocides in pigmented sponges.
Although many cellulose sponges treated with anti-microbial agents exhibit biocidal activity, many such cellulose sponges have one or more of the following drawbacks. Some treatments impact upon the viscose xanthation, regeneration and/or subsequent rinsing processes commonly utilized in sponge manufacture. Conversely, the manufacturing process may affect the treatment rendering it ineffectual. Some anti-microbial treatments adversely affect the feel, color, flexibility, texture or water sorption properties of the sponges. In other sponges, the biocidal activity is short-lived due to numerous washings that the sponge experiences during its product life. Yet, other sponges pose a toxic threat to both the environment and to humans.
Thus, there currently exists a need for an anti-microbial agent which is capable of being dispersed or formed in a water absorbing article which can maintain long-lasting anti-microbial activity. There also exists a need for an anti-microbial agent which eliminates many adverse toxic effects to humans and the environment while maintaining long-lasting anti-microbial activity. In addition, there is a need for a anti-microbial treatment of a sponge wherein the treatment does not adversely affect the feel, color, odor, flexibility or texture of the article nor does it impact upon the xanthation, regeneration, viscose or rinsing processes commonly utilized in sponge manufacture.